Terahertz detectors based on superconducting hot electron bolometers

Low noise terahertz(THz)heterodyne detectors based on superconducting niobium nitride(NbN) hot electron bolometers(HEBs)have been studied.The HEB consists of a planar antenna and an NbN bridge connecting across the antenna’s inner terminals on a high-resistivity Si substrate.The double sideband noise temperatures at 4.2 K without corrections have been characterized from 0.65 to 3.1 THz.The excess quantum noise factor β of about 4 has been obtained,which agrees well with the calculated value.Allan variance of the HEB has been measured,and Allan time up to 20 s is obtained using a microwave feedback method.Also,the intermediate frequency gain bandwidth(GBW)was measured using two dierent methods,resulting in same GBW value of about 3.5 GHz.     

角点距离矩阵和同心圆划分的曲线描述与匹配

曲线匹配对于物体识别、目标跟踪、碎片拼接等有着重要的意义。针对曲线匹配的效率与鲁棒性问题,提出了一种基于角点距离矩阵和同心圆划分的曲线描述与匹配算法。该算法分为粗略匹配和精确匹配两个阶段。粗略匹配阶段首先采用角点距离矩阵来描述曲线;然后通过子矩阵的方法来匹配曲线。精确匹配阶段首先采用同心圆划分的方法描述曲线;然后通过两条曲线同心圆描述集的差异度度量函数来度量他们的相似性。算法不仅具有平移、旋转、缩放不变性,而且具有较强的鲁棒性,可用于遮挡物体的匹配以及基于轮廓的图形拼接。实验结果表明了该算法的有效性和可行性。     

Estimating room temperatures from fires along walls and in corners

Determination of temperatures associated with room fires provides a means of assessing an important aspect of fire hazard: the likelihood of the occurrence of flashover. Layer temperatures in excess of 600°C have been associated with the occurrence of flashover. A data correlation has previously been presented to estimate layer temperatures for fires burning in the center of rooms. For fires in corners and along walls, restricted entrainment results in higher layer temperatures than predicted by the previous correlation. Modification factors for the previous correlation are developed to extend its applicability to wall and corner burning geometries. The present analysis suggests that a fire in a corner may cause flashover with only half the heat release rate necessary for a fire burning in the center of a room. Reference: Frederick Mowrer and Robert Williamson, Estimating Room Temperatures from Fires along Walls and in Corners,Fire Technology, Vol. 23, May 1987, pp. 133–145.     

基于遥感影像的变化检测技术

变化检测技术已经广泛地应用在各个领域。例如：环境监测、土地利用、农作物生长状况监测、森林采伐监测、灾情估计等方面。主要讨论了基于遥感影像的变化检测技术的实际应用。     

角接接头焊缝外观检查质量标准的探讨

针对厚壁管角接接头多次出现裂缝,解剖后又没有发现足以引起裂缝的除未焊透外的其它焊接缺陷的情况,认为除应力集中外,角接接头本身的强度也是决定是否会开裂的一个重要原因,为此建立了一个数学模型,同时结合实例证明.按目前大多数人认可的角接接头焊脚的定义,根据DL/T869-2004<火力发电厂焊接技术规程>去控制焊接尺寸,会出现焊缝有效厚度不足的问题.从而根据角接接头有效厚度不应小于最小壁厚的观点,提出对此类角接接头焊缝外观质量控制的几点意见.     

A 5 GHz LC-VCO frequency synthesizer for unlicensed band of WiMAX

This paper presents a low power and low phase noise CMOS integer-N frequency synthesizer based on the charge-pump Phase Locked Loop (PLL) topology. The frequency synthesizer can be used for IEEE 802.16 unlicensed band of WiMAX (World Interoperability for Microwave Access). The operation frequency of the proposed design is ranged from 5.13 to 5.22 GHz. The proposed Voltage-Controlled Oscillator (VCO) achieves low power consumption and low phase noise. The high speed divider is implemented by an optimal extended true single phase clock (E-TSPC) prescaler. It can achieve higher operating frequency and lower power consumption. A new frequency divider is also proposed to eliminate the hardware overhead of the S counter in the conventional programmable divider. The proposed frequency synthesizer consists of a phase-frequency detector (PFD), a charge pump, a low-pass loop filter, a VCO, and a frequency divider. The simulated phase noise of the proposed VCO is −121.6 dBc/Hz at 1 MHz offset from the carrier frequency. The proposed frequency synthesizer consumes 13.1 mW. The chip with an area of 1.048 × 1.076 mm² is fabricated in a TSMC 0.18 μm CMOS 1P6M technology process.     

便携式瓦斯检测仪管理系统的设计与实现

针对以人工登记为主的矿山便携式瓦斯检测仪发放和回收工作存在效率低下、工作流程繁琐及不利于管理和统计的问题,设计一种便携式瓦斯检测仪自动收发系统.该系统包括收发装置、服务器和Web客户端三部分,采用C-S和B-S共存的复合结构,以PHP作为开发语言,选用MySQL数据库.实际应用结果表明,该系统能够很好地完成仪表发放回收工作,便于科学的管理仪表,加快了矿山信息化和智能化的建设.     

在线红外检测仪在头孢噻肟酸合成中的应用

利用在线红外检测仪ReactIRTM4000在线监测以7-氨基头孢烷酸(7-ACA)与2-甲氧亚氨基-2-(2-氨基-4-噻唑基)-硫代乙酸苯并噻唑酯(MEAM)为原料,用二甲基乙酰胺(DMA)作催化剂,一步合成头孢噻肟酸的实验过程,主要考察了反应时间对反应的影响。在最佳反应条件下(催化剂用量、反应物用量、结晶pH已经优化)头孢噻肟酸的合成摩尔收率超过98%。     

基于VB6.0的红外甲烷检测仪串行通信的实现

针对煤矿安全生产中存在的瓦斯爆炸问题,该文以MSP430系列单片机为核心,设计了红外甲烷检测仪.其中着重介绍了检测仪的串行通信,编写了串行通信程序,使检测仪能实现与PC机的数据通信功能,并使用VB6.0编写了人机交互界面,以方便用户及时观察和处理数据,实现对检测仪的校准、复位和阈值设置等操作功能.实验结果表明,编写的串行通信程序能实现检测仪与PC的数据通信功能,检测仪能快速、准确地检测出甲烷气体的浓度,具有较高的实用价值.     

一种改进的VI CFAR检测器

为得到不同杂波背景下的良好检测性能,给出了一种改进的VI CFAR检测器.该检测器主要利用均值类可变性指示（MLVI）CFAR检测器和有序统计类可变性指示（OSVI）CFAR检测器的各自优点以及VI CFAR的以背景均匀程度自动选择不同检测器思想.理论分析和仿真结果表明：该检测器在均匀背景下性能基本与MLVI CFAR重合;多目标背景下具有较强的抗多目标能力;杂波边缘背景下有较好的虚警概率控制能力且运算量小,是一种稳健的检测器.